Why is it advantageous to have the fundamental standards accessible, invariable, indestructible, reproducible

Why is it advantageous to have the fundamental standards such as time and length be accessible invariable indestructible and reproducible?

reproducible:
With a predefined process, you can reproduced the standard in your own laboratory. This means it does not depend on context like time of day, rotation of the Earth, temperature, or an experiment that was not performed properly.

indestructible: if the stick which represents the meter or 1 kg shrinks or gathers dust and greasy material or is rusting the the integrity is compromised and it is not a standard anymore.

So that it's easy to get, not too different, never brakes and easily made again.